1. Field of the Invention
The present invention relates to a high-frequency module that receives and outputs multiple high-frequency signals within different frequency bands and to a communication apparatus using the module.
2. Description of Related Art
Various mobile communication systems for multiple frequency bands, such as Digital Cellular System (DCS) using a 1.8-GHz frequency band, Personal Communication Services (PCS) using a 1.9-GHz frequency band, and Global System for Mobilecommunications (GSM) using a 900-MHz frequency band, are currently used. Mobile terminals supporting these multiple mobile communication systems, for example, double-band devices and triple-band devices have been developed. Such mobile terminals are required to include high-frequency modules including switch circuits for switching the systems to be used. Such a triple-band mobile phone is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2002-43977.
FIG. 1 is a block diagram showing a triple-band high-frequency circuit for a mobile phone in related art. An example in which the 1.8-GHz DCS, the 1.9-GHz PCS, and the 900-MHz GSM are adopted as communication systems having different frequencies is shown in FIG. 1.
The triple-band high-frequency circuit for a mobile phone includes a high-frequency module 20, a transmission circuit TX (DCS, PCS) for both the DCS and the PCS, a reception circuit RX (DCS) for the DCS, a reception circuit RX (PCS) for the PCS, a transmission circuit TX (GSM) for the GSM, and a reception circuit RX (GSM) for the GSM. The high-frequency module 20 includes a diplexer 1, a high-frequency switch 2, a high-frequency switch 3, a high-frequency switch 4, LC filters 5 and 6, a surface acoustic wave (SAW) filter 7, a SAW filter 8, and a SAW filter 19.
The diplexer 1 has a function of outputting a DCS, PCS, or GSM transmission signal to an antenna ANT in the transmission and allocating a reception signal from the antenna ANT to a circuit corresponding to the DCS, the PCS, or the GSM in the reception. The antenna ANT is connected to a first port P1A of the diplexer 1, a first port P2A of the high-frequency switch 2 is connected to a second port P1B thereof, and a first port P3A of the high-frequency switch 3 is connected to a third port P1C thereof.
The high-frequency switch 2 switches between the side of the transmission circuit TX (DCS and PCS) for both the DCS and the PCS and the side of the reception circuit RX (DCS) for the DCS and the reception circuit RX (PCS) for the PCS. A first port P4A of the high-frequency switch 4 is connected to a second port P2B of the high-frequency switch 2 and a first port P5A of the LC filter 5 is connected to a third port P2C thereof.
The high-frequency switch 4 switches between the side of the reception circuit RX (DCS) for the DCS and the side of the reception circuit RX (PCS) for the PCS. A first port P8A of the SAW filter 8 is connected to a second port P4B of the high-frequency switch 4 and a first port P19A of the SAW filter 19 is connected to a third port P4C thereof.
The SAW filter 8 allows a PCS reception signal to pass through and attenuates an undesired wave other than the reception signal. The reception circuit RX (PCS) is connected to a second port P8B of the SAW filter 8.
The SAW filter 19 allows a DCS reception signal to pass through and attenuates an undesired wave other than the reception signal. The reception circuit RX (DCS) is connected to a second port P19B of the SAW filter 19.
The LC filter 5 allows DCS and PCS transmission signals to pass through and attenuates an undesired wave other than the transmission signals. The transmission circuit TX (DCS, PCS) for the DCS and the PCS is connected to a second port P5B of the LC filter 5.
The high-frequency switch 3 switches between the side of the transmission circuit TX (GSM) for the GSM and the side of the reception circuit RX (GSM) for the GSM. A first port P6A of the LC filter 6 is connected to a second port P3B of the high-frequency switch 3 and a first port P7A of the SAW filter 7 is connected to a third port P3C thereof.
The LC filter 6 allows a GSM transmission signal to pass through and attenuates an undesired wave other than the transmission signal. The transmission circuit TX (GSM) for the GSM is connected to a second port P6B of the LC filter 6.
The SAW filter 7 allows a GSM reception signal to pass through and attenuates an undesired wave other than the reception signal. The reception circuit RX (GSM) for the GSM is connected to a second port P7B of the SAW filter 7.
In such a triple-band high-frequency module, the characteristics of the elements are designed (adjusted) so as to achieve impedance matching between the transmission circuit and the reception circuit of each communication system.
In addition, in response to demands from markets, various double-band high-frequency modules each including one diplexer and two high-frequency switches are also provided, in addition to the triple-band high-frequency modules.
The double-band high-frequency modules differ from the triple-band high-frequency modules in the elements that are required and also in the mounting-electrode patterns of mounting boards on which the elements are mounted. Accordingly, when the double-band high-frequency modules and the triple-band high-frequency modules are manufactured, separate manufacturing lines corresponding to the respective high-frequency modules are required. As a result, it is not possible to use common processes and/or mounting boards between the double-band high-frequency modules and the triple-band high-frequency modules. This causes the manufacturing costs of the double-band high-frequency modules and the triple-band high-frequency modules to be increased.
For example, the switching of the switches can be controlled, such that the ports for one communication system are not used for the triple-band high-frequency modules, so as to provide the double-band support. However, even in such a case, many unnecessary parts that were intended for triple-band high-frequency modules are mounted in the double-band high-frequency modules and the double-band high-frequency modules become expensive.
In addition, when the parts of the ports for one communication system are not mounted, such as when SAW filters are not mounted in triple-band high-frequency modules to provide double-band high-frequency modules, high-frequency modules can be manufactured at costs lower than those of the triple-band high-frequency modules. However, it becomes very difficult to achieve band characteristics (for example, attenuation characteristics) necessary for the remaining two communication systems.